I would honestly say that it's because the game itself is stronger and more recognizable than the host...
When Louie hosted it, the gameplay sucked...now the gameplay is fine, but Karn (although he has moments where he does ok, and, IMHO, is better than Louie or Dawson's second time) is just so-so.
Match Game tried to recapture an era with bawdy innuendos, but it's prize shrinkage, less-than-stellar panel, and low clearances didn't help it all. Plus, All-American failed to realize that the zaniness on MG didn't come about through forcing these innuendos, they kinda just happened.
To tell the Truth did ok, but I think the era of panel shows has passed.
Card Sharks died because its not as strong of a name as Feud was, and to top it off, they screwed around with a game that probably would have been fine in its original incarnation.